The present invention relates to the general field of ignition systems for a combustion chamber of a gas turbine engine. The invention relates more particularly to a device for mounting a spark plug on a wall of a combustion chamber.
In a gas turbine engine, the combustion chamber is generally constituted by outer and inner longitudinal walls with multiple perforations that are connected together upstream by a transverse wall forming a chamber end wall. These longitudinal walls are fastened downstream to annular casings and they co-operate with the casings to define an annular space that receives air coming from the compressor. The chamber end wall has a plurality of fuel injectors passing therethrough. A fraction of the air coming from the compressor is introduced into the combustion chamber at the injectors, mixed with the fuel, and then burnt in the chamber.
The combustion chamber is ignited by means of one or two spark plugs arranged downstream from the injectors. The spark plugs are typically fastened to the outer casing and they have free ends that pass through the outer wall of the combustion chamber. At its free end, each spark plug is mounted more specifically on the outer wall of the chamber by means of a mounting device that accommodates the relative movements that can exist between the casing and the wall of the combustion chamber on which the spark plug is mounted.
That type of mounting device generally consists in a chimney welded to the outer wall of the combustion chamber, and a spark plug guide that receives the free end of the spark plug and that is floatingly mounted inside the chimney so as to accommodate relative movements between the casing and the wall of the chamber. By way of example, reference may be made to document FR 2 927 367, which describes an embodiment of such a device.
Furthermore, during the operation of making multiple perforations in the walls of the combustion chamber by means of a laser, it is necessary to install protectors around the mounting devices in order to prevent the laser beam from damaging the assembly comprising the chimney and the spark plug guide. Such protectors have a certain amount of thickness, which has an influence on the total height of the mounting device.
Unfortunately, in certain engines, the space available for housing a spark plug mounting device between the outer casing and the outer wall of the combustion chamber is limited. There therefore exists a need for mounting devices that present small radial size, i.e. in which the height of the chimney and spark plug guide assembly is significantly reduced, while still allowing protectors to be installed.